Rattling noise on Puma 80e after HW/CH turned off

[ciaran61]

Hi all,

The Low Pressure light on my Potterton Puma 80 combi boiler recently came on and the boiler stopped firing up for both HW and CH. I checked the pressure and sure enough it was around 0.5 bar. I topped it up to around 2 bar (where my red pointer is) using the filling loop, but the Low Pressure light stayed on and the boiler failed to fire. I topped it up till it was at 3 bar but still no joy.

After searching this forum for hints it sounded like the Pressure Switch may be stuck or broken. I disconnected this on the PCB, turned a hot tap on and hooray, the boiler fired up! However whilst reading around I realised I'd been foolish in letting the pressure get so high, so I bled the radiators till the pressure was 1.5 bar.

HW and CH are working, but the problem is that the boiler makes a loud rattling noise when the taps are turned OFF. While they're on it's making the "normal" amount of noise it always has. I turned the CH on for 30-45 mins and again it made a normal amount of noise, but after a while it started rattling, getting progressively more unsettling and louder until I turned it off. The radiators do get hot and there's hot water coming from the taps, so it's just the noise and the stuck/broken Pressure Switch that are worrying me.

Any help would be much appreciated!

Yours shivering,

Ciaran

EDIT: Just to add - the HW & CH were working fine until a couple of days ago, before the Low Pressure light came on.

I also turned off the mains water recently to fix a leak with the dishwasher. A few days before the Low Pressure light came on I had to loosen the mains stop cock as the cold water pressure was too low.

 

[baxpoti]

The pressure switch can be cleaned internally,

to do so,
drain system, remove switch, there will probably be a black 'dot' in the middle of the brass base, use a small sharp instrument to remove this 'dot' it's actually a hole about 10mm deep, finally flush under clean cold water and refit etc

A new fan will quieten a Puma considerably (its never been so quiet)

but your noise is more than this!

Is it a water/boiling/air noise? or metallic/grinding noise?

 

[ciaran61]

Hi baxpoti, thanks for the advice, I'll take a look at the pressure switch tonight.

I had a proper listen to the noise last night and it sounds like a rotor blade (as on a fan or pump) that's blocked. It doesn't sound like "kettling" as it's not a banging, explosive noise or popping noise, more a rhythmic rattle with a bit of a whine! God noises are hard to describe!

So the fact it was rhythmic made me think it might be the pump, so I had a listen to it and it certainly seems to be coming from that direction. It gets damn hot too, but since I know little of how boilers work, I presumed that could be because it's pumping hot water! Does the pump operate when ONLY the HW is on and does it continue to do so for a minute or so after the HW is turned off? Or is this the fan I'm hearing?

 

[baxpoti]

With a cold boiler check the pump spindle (big black nut on the front of pump) is free (have a rag ready) it should spin easily and continue to spin freely when you let it go for a few seconds.

If its a permanent pilot the fan runs continuosly (albeit at low speed when no demand)

I would go for the pump first as this is a much cheaper option

 

[ChrisR]

It's just possible your pressure relief valve started letting out water when you got it to 3 bar, and is therefore still doing it (cos they do ), making a noise. Check the pipe outside. You would also be losing a bit of pressure, but sometimes not a lot.